1. Field of the Invention
The invention relates to an electrical drive system for the synchronised adjustment of a plurality of rotatable axles or further, also linearly movable functional parts of devices and machines, in particular printing machines, in terms of their position, speed or acceleration. A plurality of drive units controlled using computer assistance are connected, according to the single drive technique which is known per se, to one or more functional parts for their adjustment.
2. Description of the Related Art
In this context, it is known (Patent DE 196 33 745 C2) to form a plurality of separate drive networks, which respectively have a plurality of the said drive units as network nodes. The communication of these drive units with one another is carried out via a parallel bus system. Since, for example in the case when newspaper printing machines are being used, from 100 to 200 drives to be synchronised are by no means uncommon, this known patent proposes that a plurality of such drive networks be formed separately from one another and, according to a section of the machine or system, these individual drive networks be interlinked with one another via a cross- or intercommunication network and that they be synchronised, above all with one another, on a common master axis. For the intercommunication network, a ring topology is proposed with the communication taking place in accordance with the master/slave principle (cf. SERCOS interface, known per se). In this case, the bus masters of the respective drive networks form slave nodes of the intercommunication network, and a further bus master also functions as the bus master of the intercommunication network. In order that further machine sections can be synchronised with the aforementioned machine section, the patent also proposes that the bus master of a first intercommunication network specify a synchronous clock via its master synchronisation telegrams, not only for the slaves of its network but also, via a communication interface inserted as an additional network node, for the neighbouring master/slave intercommunication network. The communication interface is in this case simultaneously a node of the neighbouring network. It is therefore possible for setpoint values, generated at a master level, to be distributed to a multiplicity of drives running in angular synchronism. Stringent requirements in terms of synchronisation can hence be satisfied. Even time shifts of the setpoint values by one μs lead at a high production rate (for example 35,000 print copies per hour) to an angular error of 3.5 millidegrees. On a printed paper, this can cause an offset between two colours of 0.01 mm (if the printing roll has a circumference of approximately 1100 mm) with corresponding disadvantages for the printing quality. However, the use of a parallel bus structure according to the patent in the respective drive networks leads to a high outlay on transmission and cabling. This disadvantage is exacerbated further when significantly large distances need to be covered.
To help, the drive system specified in Patent claim 1 is proposed, which is distinguished from the said previously published patent by the fact that the drive units or nodes of the drive network are arranged in accordance with the master/slave principle and are respectively connected to one another in a ring structure through communication channels and/or a communication system. With the master/slave ring structure, the individual nodes or drive units can advantageously be set for synchronisation to a common clock, with minimal outlay on cabling and installation. Furthermore, it is possible to cover larger distances than with the previously known use of the bus topology.
In relation to the drive system disclosed in the aforementioned patent, there is furthermore the requirement for increased reliability, availability and maintainability. In multi-axis applications, for example in printing machines, it is necessary to ensure that the failure of individual drive units, drive networks or of the intercommunication network interlinking them does not lead to failure of the entire machine system or of the entire drive system. Besides this, also to increase availability and maintainability, there is the further requirement that both logical and physical drive groups or networks can be formed with high flexibility. Therefore—to increase availability—it should be possible to switch off individual machine parts or machine systems without affecting the rest of the machine.
It is also an aim of the invention that, beyond the actual hardware network configuration, in principle any drives can be combined into logical groups or networks, to which different setpoint values are then applied. In the case of using printing machines in which each folding mechanism usually specifies a master axis, it should be possible to synchronise each printing mechanism with any folding mechanism for the definition of a paper web.
A further requirement is to supply drive groups with additional setpoint values which are independent of a centrally specified master axis and which are processed, while being synchronised with one another, in the drives allocated to this master axis. In the case in which printing machines are used, this function is typically needed for adjustment of the cutting register.
Furthermore, for so-called set-up operation and various synchronising functions, there is the requirement for group formation which takes place independently of the respective master axis allocation.
A further requirement is to increase the diagnosability as well as the modularity of the electrical drive system.
In order to meet these requirements, in the scope of the general inventive concept, the electrical drive system specified in Patent claim 2 is proposed, which is distinguished by a plurality of intercommunication networks coupled with one another for the purpose of data and/or command interchange. Their nodes, which are communicatively coupled with one another, simultaneously belong to different drive networks. A multi-link controller is furthermore arranged, which has communication components or interfaces that each form the respective nodes of one of the intercommunication networks. This makes it possible for the individual intercommunication networks to be connected modularly and flexibly, interlinked logically, coupled or managed, which is carried out via a corresponding design, using program and/or circuit technology, of the multi-link controller.
Owing to this drive system according to the invention, the failure of an intercommunication network or of an allocated machine or system section does not cause the rest of the communication, which is taking place via the multi-link controller, to come to a standstill. The failed network and/or the failed machine section, after repair and with restarting, can again join in the data and command interchange in the multi-link controller. On the other hand, if the multi-link controller fails, each machine section or the associated intercommunication network can continue to run independently until, for example, defective cards or modules have been replaced. Owing to the structure according to the invention, it is possible at any time during continuous operation for intercommunication networks with associated machine sections to be isolated from the communication chain for maintenance work, which increases the maintainability.